Thesis (M.S.) University of Alaska Fairbanks, 2004A semi-analytical method is presented to predict the shear stress and motion resistance at the tire/snow interaction. The shear stress model is a function of normal pressure and slip. The main goal was to develop a simplified model by reducing the number of parameters in the model, so that the computational time could be reduced towards real time simulations. Motion resistance is calculated by integrating the horizontal component of normal pressure along the tire/terrain contact surface. The motion resistance obtained is slip dependent because the sinkage is a function of slip. The calculations of motion resistance and sinkage were done using the presented model and an existing model. Also the calculated results were compared with the FEA (Finite Element Analysis) data, which matched reasonably well. In the second part of the thesis shear force is expressed as a function of normal load, slip and slip angle. Shear force parameters tire stiffness, friction coefficients, and contact pressure constants were assumed as the functions of normal load and the coefficients of parameters were found through curve fitting using FEA data. These functions were used to calculate tire stiffness, friction coefficient and contact pressure constant. The calculated results matched well with FEA simulation results for the same tire and snow conditions. Pure shear force and the combined shear force were compared, and the pure shear force is always greater than the combined shear force for the same slip and slip angle.1. Introduction -- 2. Review of tire/snow interaction models -- 3. Parametric analysis of shear forces -- 4. Semi- analytical shear stress model for shallow snow -- Conclusions and future work -- References -- Appendix
